need help small help: pc restarts by itself after hours of downlding

[ante1]

hello for evry one and hello big one for people who made limewire
now my broblem with limewire is
when i am open lime wire and searsh and start download
after about 1 or 2 or 3 hour my pc restart it self (why??)
i try stay my pc on with out lime wire for 6hour and my pc did not get restart ...
so the broblem is lime wire or my pc or my windows
any way my pc is good cuz i try let my windows open for hour s
my windows is xp sb2...
pls help me
another one when i am get restart all my download in lime wire away...and tell me in the massage
that lime wire cannot complete the download...
so i need to re start my download that make me crazy ...cuz if a file 200mg and now in downlad before restart 110 and lime wire wanna me re download it is disaster
so why my pc restart it self when using lime wire
and why my download cannot combleat when my pc get restart it self
need sove 2broblem and i am waiting
some thing more lime wire is greaaaaaaaaaaaaat.
2222222222
my lime wire is
LimeWire 4.9.28
my pc is
p4/300cbu/512ram/msi-mothar